A typical side-gusset bag has a front panel, a rear panel, and side gussets between the front panel and the rear panel and connected to the front and rear panels by respective edge folds. The side-gusset bag is made of a plastic film/fabric laminate that comprises a polymer film on the outer surface of the bag and fabric connected to the polymer film and made of polymer ribbons on the inner surface of the bag. The fabric and the polymer film on the outer surface of the bag are connected flatly to each other and form a fixed plastic film/fabric laminate. The side-gusset bag that lies flat is closed on one end by a lower end flap of the front panel, and side-gusset flaps between the flap of the front panel and the rear panel and folded onto the rear panel to form a bottom gusset and connected thereto. The front and rear panels form surfaces of equal size. The designation of these bag surfaces as “front panel” and “rear panel” is intended to facilitate understanding of the teaching according to the invention, and not to present any technical restriction. For the purpose of facilitating understanding of the technical teaching as claimed, in the scope of the disclosure of the invention, the bag surface onto which film flaps are folded and attached, thereby forming the bottom gusset, is termed the “rear panel.”
The flattened side-gusset bag can be filled through the open end thereof, and is closed following filling. The filled side-gusset bag is configured as a packaging bag, particularly for loose fill materials such as pelletized animal feed, litter for animals, or similar materials. As a result of the use of a plastic film/fabric laminate, the side-gusset bag is particularly suitable for large packages that have a significant filled volume and a significant filled weight. Corresponding side-gusset bags are also termed “side fold bags” in practice. No differentiation is made between these two terms in the context of the present invention.
Side-gusset bags made of single- or multi-layer films not reinforced by a fabric typically have a bottom face formed by welds. The welds extend from a edge fold on longitudinal sides of the front or rear panels, at an acute angle, toward the bottom gusset. The welds, also termed “corner seals”, function such that the base of the side-gusset bag better forms a flat bottom face when the side-gusset bag is filled with a product.
In practice, side-gusset bags manufactured from a plastic film/fabric laminate do not have any welds to shape the base, because the fabric surface on the inner surface of the bag cannot be welded, or cannot be welded well. High welding temperatures are necessary to produce a weld, and there is the risk that the polymer structure and the orientation of the polymer ribbons of the fabric will be destroyed by to much heat. A further problem in the creation of welds between the flanks of the side gussets and the adjacent front panel or rear panel is the poor contact between the surfaces being connected, due to their fabric structure. Side-gusset bags made of plastic film/fabric laminate materials, and without corner seals on the bottom face, have a base shape that is visually poor following filling. The poor base shape also has negative influences on the volume of the container, because the fill height increases if the base does not sit correctly. This then needs to be taken into account by increasing the height of the bag. The problem occurs particularly in the case of side-gusset bags that lie flat, and have deep side gussets that form rectangular packages after filling.
In order to make it possible to create welds on side-gusset bags manufactured from a plastic film/fabric laminate, the fabric must be equipped over its entire surface or at least sectionally with a coating capable of producing a weld—produced by way of example by an extrusion coating or by the application of a hot-melt glue. The use of coated fabrics made of uniaxially oriented polymer ribbons, and a coating made of a sealable polymer, for the purpose of producing bags, is known from US 2010/0209024. The coating of the fabric surface of a plastic film/fabric laminate material, for the purpose of improving the seal properties, involves a complex manufacturing process, and requires an additional application of material that involves accordingly higher costs.
The practice of connecting a fabric made of polymer ribbons to a polymer surface, by ultrasound welding, is known from U.S. Pat. No. 4,373,979. The fact that the ultrasound welding method can be used to close the end of the film tube is described using the example of a side-gusset bag. The weld points produced by ultrasound welding are in multiple rows that extend perpendicularly to the longitudinal direction of the film tube. In this case, the distance between the weld points is selected such that each polymer ribbon of the fabric is captured by one weld point.